I use them all the time on my Baritone/treble , leaning back against them when playing chords at the lower end and they help to control this 8" Octagonal instrument which has centrally located thumbstraps, as opposed to the normal 'towards the lower notes' position.

I also use wrist straps on my small EC if I have to play standing up for longer periods ( street animations etc).

I need extra wrist support (owing to old RSI) and my EC has straps added. It is a Lachenal treble and they help me a lot. Some people may not need them (some people aren't prone to carpal inflammation).

I noticed that some ECs have wrist loops as well as thumb straps and pinkie rests.

On photographs these seem to be larger than the wrist straps on Anglos and Duets.

I would be interested to hear if these are useful and how they are used.

Apologies, Don, but first I'm gonna nitpick your choice of words, though I acknowledge that you're hardly the only "offender" in that regard :

Your EC "wrist loops" are normally referred to as "wrist straps". They do not form closed "loops", unless you count the body of the concertina as part of the loop.

On the other hand, the straps on anglos and duets go across the back of the hand and I've never seen one contact the wristwhile an instrument was being played

And I'll once again contend that the plate for the little finger does not function as a place for that finger to passively "rest", not even for folks whose little fingers play a less active role than mine in holding and controlling the end of the instrument.

But enough of that. To answer the question, some players report that they find wrist straps on an English to be useful. I have tried them, and I don't. So I would suggest that their "utility" is something of an individual thing, like preference for anglo vs. English, or maybe like preferred fingerings for particular passages. In any case, those who do use EC wrist straps have already started reporting how and why they use them, so that should help to answer your question. But it's important to be aware that the function of EC wrist straps is quite diffferent from that of anglo/duet hand straps, and this is reflected in the fact that both the means and location of their respective attachment are quite different.

I understand your disputing my choice of words - I struggled to know what to call these things as they are really not the same as what we call 'wrist straps' on Anglos or Duets. Maybe if we renamed those on Anglos and Duets as 'back of the hand straps' then we could call the straps on ECs 'wrist straps' because, well, they go around the wrist.

Maybe I can call them EC support straps, although that has a rather medical tone to it.

Anyway, to clarify what I am asking about, here is a picture of some EC support straps on an instrument that recently sold on eBay:

I noticed that some ECs have wrist loops as well as thumb straps and pinkie rests.

On photographs these seem to be larger than the wrist straps on Anglos and Duets.

I would be interested to hear if these are useful and how they are used.

Wrist straps were used on my Tenor-treble and my Baritone-treble but I often did not use them because they were restricting when I played chords in the lower range.

Just to clarify, I used the straps when the music permitted, but there were some chord configurations that were not possible when constrained by the straps. They did offer additional leverage when drawing open the bellows. I never used them for supporting the weight of the instrument. I eventually removed them from the TT because they were in the way in my opinion. I might have a different opinion if I were playing while standing, but that's never happened.

Straps,loops, who cares what they're called, they're very useful for me. I get tendon problems in the thumbs so the straloops diminish the pressure on the thumbs when drawing the bellows. I have the straps attached at the top by the same screw used for the thumbstrap so they actually do come across the lower back of the hand. Don't any problems playing or chording the lower register notes.

I always had aching thumbs when playing my EC until I did this modification. It did not have to bore additional holes and I used spare bits I had at home. Only the design leaves sth to be desired, I am very happy otherwise.